The present invention relates to a mechanical accumulating conveyor operable to advance articles located behind an empty station to their next successive stations to ensure that any empty station will be filled by an article. In particular, this invention relates to shuttle type accumulating conveyors where articles are pushed from station to station rather than being lifted at one station, carried to the next station and deposited there.
U.S. Pat. No. 4,349,099 discloses a lift-and-carry type accumulator which has performed satisfactorily. The accumulator disclosed therein commprises an elongated support along which a series of stations are provided, a transfer bar on which feed units and feed unit setting assemblies are provided, and coacting article sensors and actuator members which are positioned on the support at each station. The work cycle begins with a rearward movement of the transfer bar, which causes all feed units to the rear of an empty station to be raised to their feed positions. The transfer bar is then raised so that the feed units lift all of the articles to the rear of the empty station. The transfer bar is then moved forwardly a distance equal to the distance between stations, then lowered to deposit articles at their next successive stations. Subsequently, the transfer bar is moved rearwardly again and all feed units are moved out of their feed positions before the start of the next cycle. Machines of this type have performed with excellence. However, there are several advantages to shuttle type accumulators and it is a general object of the present invention to provide an improved shuttle type accumulator which utilizes the principles of the aforementioned U.S. Patent.
The principal advantage of shuttle accumulators over lift-and-carry type accumulators is that the former require a much simpler motion of the transfer mechanism. In general, a transfer bar in shuttle accumulators need only move forward and rearward and need not travel up and down. Thus, a shuttle type accumulator may be simpler to operate and less costly than a lift-and-carry type accumulator.
However, several problems have been encountered in shuttle type conveyors. First, it is found that, since the feed units must be initially positioned behind the articles in order to push them to the next stations, the transfer bar must travel a distance greater than the distance between stations. Parts attached to the transfer bar, such as the feed unit setting assemblies, tend to interfere with parts attached to the support, such as the actuator members, when the transfer bar moves to its full forward position. This can cause the drive mechanism to bind or stall. It is another object of the present invention, therefore, to provide a shuttle type accumulating conveyor in which such a binding problem is avoided.
Another problem encountered in shuttle accumulators is in the mechanism which resets the feed units prior to the start of a work cycle. In lift-and-carry accumulators, each feed unit setting assembly is moved in a forward direction only while the transfer bar is raised, overpassing a knockdown lug. On the return stroke, the transfer bar is lowered and the feed unit setting assembly engages the knockdown lug and this causes the associated feed unit to be reset. In a shuttle type accumulator, in which the transfer bar is not raised and lowered, the feed unit setting assemblies engage the knockdown lug on both the advance and return strokes. It is another object of the present invention, therefore, to provide an improved shuttle type accumulating conveyer wherein the knockdown problem is overcome.